package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

@Component
@Slf4j
public class CacheClient {
    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    //设置过期时间
    public void set(String key, Object value, Long time, TimeUnit unit)
    {
        //其中的value是任意对象，使用json工具将其序列化
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value),time,unit);
    }

    //设置逻辑过期时间
    public void setLogic(String key,Object value,Long time ,TimeUnit unit)
    {
        //设置过期时间
        RedisData redisData=new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //添加到redis中 在redis中的对象中可以直接读取
        stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(redisData));
    }

    //解决缓存穿透
    public <R,ID> R querryWithPassThrough(
            String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallBack, Long time, TimeUnit unit
    ){
        String key=keyPrefix+id;
        //首先从redis查询
         String s = stringRedisTemplate.opsForValue().get(key);
         //判断是否粗在
        if(StrUtil.isNotBlank(s)){
            return JSONUtil.toBean(s,type);
        }
        //判断是否为空先返回,然后去重建缓存
        if(s!=null)
        {
            return null;
        }
        //查询数据库
        R apply = dbFallBack.apply(id);
        if(apply==null){
            //将空写入redis中
            stringRedisTemplate.opsForValue().set(key,"",2,TimeUnit.MINUTES);
            return null;
        }
        this.set(key,apply,time,unit);
        return apply;
    }

    //解决缓存击穿问题
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public <R,ID> R queryWithLogicalExpire(
            String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallback, Long time, TimeUnit unit) {
        String key = keyPrefix + id;
        //1.从redis查商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(json)) {
            //3.存在，缓存中存的null
            return null;
        }
        //4.命中，先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //5.1未过期，直接返回店铺信息
            return r;
        }
        //5.2已过期，需要缓存重建
        //6.缓存重建
        //6.1获取互斥锁
        String lockKey = RedisConstants.LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //6.2判断是否获取锁成功
        if (isLock) {
            //6.3 成功，再进行二次判断，查看缓存中是否有数据，因为有可能是别人刚刚重建完释放锁，刚好获取到了

            //6.4 开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //查询数据库
                    R r1 = dbFallback.apply(id);
                    //写入redis
                    this.setLogic(key, r1, time, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unlock(lockKey);
                }
            });
        }
        //6.6返回过期的商铺信息
        return r;
    }
    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }
}



